More than 160 academics have written to the Guardian to protest at being used as an extension of the UK border police, after universities have come under more pressure to check the immigration details of students.

The academics, from universities including Oxford, Warwick, Durham and Sheffield, accuse the Home Office immigration agency of "undermining the autonomy and academic freedom of UK universities and trust between academics and their students".

Unrest has been growing for months as universities have come under more pressure to prove that their students are legitimate, according to the signatories, who say matters took a "pernicious new turn" in summer 2012 when London Metropolitan University briefly lost its trusted sponsor status – a requirement for all institutions wishing to recruit overseas students.

"Since then, universities have been preoccupied with managing accountability demanded by UK Visas and Immigration (UKVI – formerly the UK Border Agency), and in effect have become its proxy," says the letter. "Academics at a number of universities in the UK and beyond have now become concerned at this state of affairs, and at the methods used to establish bona fide student status."

Academics are being asked to monitor attendance and in some cases potentially to share emails with UKVI, said Mette Berg, of the Institute of Social and Cultural Anthropology at Oxford University. "We have a duty of care towards our students, and there is an issue about this undermining the trust between tutor and student. We are not there to be proxy border police."

A Home Office spokesman defended the reforms to the student visa system, saying they had made the application process more rigorous and less open to abuse.

The academics say the changes come at a time when universities are becoming more reliant on the fees of non-EU students. The letter says: "British universities have been positioned as central culprits for failing to regulate their intake of foreign students, while rendered dependent on overseas student fees because of government funding cuts."

Nicola Pratt of Warwick University said some vice-chancellors were so concerned about losing their ability to take foreign students there was a danger of checks becoming heavy-handed.

"We are a community of scholars and students, and those students should be judged on the basis of academic merit, not on the basis of their visa status," she said. "It is a major concern that the government is targeting overseas students as a way of meeting immigration targets, especially as these students are investing a huge amount in the higher education system."

The letter calls for an end to the monitoring of students via sessions designed for pastoral care, and for UK, EU and non-EU students to be treated and valued equally. It also asks for Universities UK, an advocacy organisation for universities, to speak out against monitoring students.

"We call on Universities UK, on behalf of member university vice-chancellors and principals, to oppose the discriminatory treatment of non-EU students in all forms and publicly affirm that the quality of academic work should be the primary criterion for determining academic standing," the letter says.

Nicola Dandridge, chief executive of Universities UK, said it was not acquiescing to the demands of the Home Office but had worked with it to make immigration compliance measures reasonable.

"We have been clear with the Home Office that attendance monitoring should not impact on students' experience at university nor detract from the UK as a welcoming destination for international students," she said.

"It is reasonable to expect universities to take responsibility for ensuring that students are engaged with their studies. This applies to all students, and not just international students."

The Home Office said: "We continue to welcome the brightest and the best students and the latest statistics show that visa applications from university students has risen by 7% in the year ending December 2013. It is only right that universities adhere to the guidance and immigration rules of sponsorship by taking reasonable steps to ensure that every student has permission to be in the UK."